The present application generally relates to rotary shaft seals which prevent lubricants associated with shaft bearings from leaking externally of the bearing housing or bearing support as well as for preventing foreign particles in the environment from working themselves through the seal into the lubricant, more particularly, to labyrinth and other dynamic type rotary shaft seals designed for such purposes and most particularly, to an improved rotary bearing isolator seal having two reusable/rebuildable stator components and a sacrificial/replaceable rotor component.
Typical prior labyrinth type rotary shaft seals are shown in Rockwood, et al. U.S. Pat. No. 4,572,517; and U.S. Pat. Nos. 4,022,479, 4,114,902, 4,175,752, 4,304,409, 4,706,968, and 4,466,620, all to Orlowski. In such typical labyrinth type seals, interior labyrinth type grooves are provided in a metal seal ring which is fixed to a bearing housing. These grooves are specifically contoured to create a hydraulic dam effect that acts to remove lubricants moving axially along the shaft and pass them back into the bearing housing. Additionally, such labyrinth type seals are provided with sealing rings for preventing material from moving internally into the housing. However, a problem associated with this type of conventional seal is that there is no complete seal between the interior and exterior sides of the seal so that some material is permitted to move through the seal into the bearing housing. Furthermore, since the sealing ring wears due to the rotation of the shaft relative to the sealing ring, eventually a state is reached where sufficient foreign particles have entered the housing which leads to damage of the shaft bearings. Furthermore, labyrinth type seal designs are ineffective when shaft conditions exist such as misalignment (a condition where the center line of the shaft is displaced perpendicularly (or radially) with respect to the center line of the bore of the bearing seal) and run out of the shaft (a condition where a radial rotational eccentricity exists due to bearing wear, shaft bending or warping, etc.).
As an alternative to the labyrinth groove type seal, rotary shaft seals are known which utilize a seal member that is disposed within a seal housing and which has one or more flange-like lips biased into engagement with a wall of the seal housing. However, since the sealing member is fixed onto the periphery of the rotating shaft so as to rotate with it, high frictional forces are created at the interface between the free end of the flange-like lip and the nonrotating wall of the housing against which it is biased. Examples of such shaft seals can be found in Otto U.S. Pat. No. 3,368,819; Romero U.S. Pat. No. 4,428,586; Johnston U.S. Pat. No. 4,462,600; Toyoda, et al. U.S. Pat. No. 4,465,285; Wehrfritz, et al. U.S. Pat. No. 4,565,378; and Symons, et al. U.S. Pat. No. 4,572,516. With such seals, even if centrifugal forces are utilized to vary the contact force of the flange-like lip against the housing so as to reduce the contact force with increasing shaft speed (see, for example, the above-indicated Toyoda, et al. and Symons, et al. patents), ultimately sufficient wear occurs as to defeat the effectiveness of the seal to such an extent as to require replacement thereof. On the other hand, while it has been proposed to have a flange-like seal lip serve as a contact seal only when the shaft is stationary or rotating slowly, the lip being lifted from the housing wall against which it engages upon a predetermined increase in the rate of shaft rotation (see the above-mentioned Wehrfritz, et al. patent), such a seal has required the use of a compressed gas to lift the flange-like lip and prevent the ingress of foreign matter at higher speed conditions. Such a seal also requires a labyrinth arrangement to prevent the ingress of compressed gas into the bearing and the egress of lubricant from the bearing, at such increased shaft rotation speeds, creating a costly and complicated sealing arrangement.
Recently, Borowski disclosed in U.S. Pat. Nos. 4,852,890 and 4,817,966, the disclosure of each is herein incorporated by reference, a bearing isolator seal assembly that was simply and economically constructed, yet effectively eliminated both the movement of bearing lubricant from the seal housing and the movement of foreign particles into the bearings and lubricant from outside of the housing, and provided a relatively long wear life. However, these prior rotary shaft bearing isolator seals were designed to be replaced as a unit, i.e. both the stator components and the rotor component were replaced when the rotor component sufficiently deteriorated from wear to such on extent as to require replacement of the entire unit, both stator components and the rotor component.
While the improved bearing isolator seal assembly of Borowski has proven at least partially effective in most applications, nevertheless one of the disadvantages of such assemblies is the relatively complex configuration of the interior and exterior stator as well as the rotor and the consequent cost of the manufacturing thereof. Further, many of the prior devices, including Borowski because of the manner of interfit and cooperation between the stator and rotor, have required that at least some parts be of a split construction, thereby maintaining high manufacturing and assembling complexities and cost.
Since the rotary shaft bearing isolator seal assembly disclosed in U.S. Pat. Nos. 4,852,890 and 4,817,996 did not address the issue concerning the relatively short wear life of the rotor component as opposed to the stator components of the seal assembly, there is still a need for an improved bearing isolator seal for rotary shafts or bearing isolator seal assembly which can be simply and economically constructed, yet effectively eliminates both the movement of bearing lubricant from the seal housing and the movement of foreign particles into the bearing and lubricant outside of the housing and provides a long wear life. Further, such improved rotary shaft bearing isolator seals should include a mechanism that allows the rotor portion to be easily and accurately initially assembled into a selectively connected and disconnected two-piece stator and that provides for the easy removal and replacement of a worn rotor by a new rotor member in the original stator member upon the initial rotor member having undergone sufficient wear to reduce the seal effectiveness. Such improved rotating shaft isolator seals having replaceable rotor components reduce manufacturing, assembly and maintenance costs and reduce manufacturing, assembly and maintenance complexities.
In view of the foregoing, it is a primary objective of the present application to provide improved rotary shaft isolator seals which are simply and economically produceable and usable, while being effectively wear-free in terms of their ability to prevent lubricant leakage and foreign particle entry and include a replaceable rotor component.
It is a further object of the present application to provide an improved rotary shaft seal that includes a readily replaceable flange-like sealing element or rotor component to prevent lubricants and foreign particles from traveling through the seal under dynamic conditions, but not under static conditions.
Another object of the present application is to provide an improved rotary shaft seal structure which, under dynamic conditions, extends the life of the selectively replaceable rotor component by selectively adjusting the clearance between the rotor and the stator as the rotor component wears.
Still another object of the present application is to provide a replaceable rotary shaft bearing isolator seal including a replaceable rotor component and reusable stator components which will allow for both static and dynamic sealing at either one or both sides of the seal housing.
These and other objects of the present invention are achieved in accordance with preferred embodiments wherein an improved rotary bearing isolator seal has a shaft seal assembly comprising a two-piece, selectively removably connected stator and a selectively removable rotor operatively positioned in the selectively assembled and disassemblable stator. The two-piece, selectively connected or disconnected stator has an inner radically extending face with an annular flange of substantially frusto-conical shape that extends from a larger diameter end that is fixed to the inner radially extending face to a smaller diameter free end. The selectively replaceable rotor has a peripherally extending radial flange of substantially frusto-conical shape that is provided with a smaller diameter end that is fixed to a hub of the rotor, a larger diameter free end, and a contact sealing surface there between. The larger diameter free end is biased into contact with the inner radially extending face of the stator housing and the contact sealing surface is biased into contact with the free end of the annular flange of the stator housing in a manner causing these areas of contact to be broken under the effect of centrifugal forces generated by rotation of the rotor with the shaft.
In accordance with one embodiment, a pair of annular flanges cooperates with a pair of radial flanges which are arranged in a mirror image relationship, thereby enabling static and dynamic sealing at both sides of the seal.
In accordance with other aspects of the invention, the improved rotary isolator seal can be formed of three or four components with the stator having two parts selectively connected together with a rotor there between which can be removed from its initial position between the two stator components and can be replaced by another rotor component.
In accordance with these and further objects, one aspect of the present invention includes a rotary shaft isolator comprising: a stator having a first component and a second component; a rotor having a radial flange for engaging a surface to be sealed; and means, operatively positioned on the first and the second stator components, for operatively selectively, disconnecting and connecting the first and the second stator components such that the rotor can be initially operatively positioned between the first and the second stator components and then selectively removed from the stator and replaced by a new rotor operatively positioned between the first and the second stator components.
Another aspect of the invention involves positioning the rotor between the stator components such that their spatial relationship can be utilized to obtain any desired clearance.
Other objects, features and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.